Innervation may play an important role during secondary induction in the morphogenesis of orofacial ectodermal derivatives such as taste receptors. The overall hypothesis to be evaluated is that in mammals nerves are required not only to maintain the integrity of lingual gustatory papillae but also to induce taste bud differentiation. To evaluate the effects of the absence of innervation on the survival of gustatory papillae and the differentiation of taste buds, 12 and 13 day embryonic murine tongues will be cultured for 10 days. Patterns of fungiform papilla development will be analyzed in these cultures and compared to those of short term cultures. Since evidence for regeneration experiments suggested that innervation regulates taste bud differentiation, the effects of sensory innervation of fungiform papilla integrity and taste bud occurrence will be studied in presence of either geniculator or trigeminal ganglion. The experimental design will include using cocultures and a novel technique of combined cultures of 12 day embryonic murine tongue explants and geniculate or trigeminal ganglion. In cocultures, tongue and the pertinent ganglion will be explanted and then recombined in cultures, whereas in combined cultures, tongue and sensory ganglia will be removed as a whole from embryos to maintain the nervous connections between tongue and the ganglia during the explantation. To increase survival times of the neurons from cranial sensory ganglia, cultures will be supplemented with neurotrophins, BDNF and NT3. The effects of varying concentrations of BDNF and NT3 on the maintenance of fungiform papillae and the differentiation of taste buds will be established. These studies will provide insight into the role of innervation in the maintenance and differentiation of ectoderm- derived sensory receptors. Such understanding may offer a basis for therapeutic advances in the prevention and treatment of sensory function losses associated with aging, degenerative diseases, and trauma.